Worst abuse of the C preprocessor

Judges' comments:

Compile this program and feed ascii text into standard input. This
program is known to pass lint on some systems and abort lint on
others.

This program was selected for the 1987 t-shirt collection.

Think morse code when you ponder this program. Note how use of
similar variables can be obfuscating! The author notes that this
program implements the international morse standard. Now for extra
credit, what morse message does the program spell out?